Human blood includes both cellular and non-cellular components. The cellular components in blood include red blood cells (RBC), white blood cells (WBC), and platelets. Plasma is a non-cellular component of blood and is the liquid medium in which the cellular components are suspended. Plasma also includes various other components such as proteins, compounds that assist in blood coagulation (coagulation factors), electrolytes and metabolites.
During or after collection, human whole blood is commonly separated into its various components (RBC, WBC, platelets, plasma). Typically, the separated components may be stored for some period of time, and transfused to a patient in need of a particular blood component. For example, collected plasma may be transfused to a patient to provide plasma proteins and coagulation factors, or to replace lost blood volume. Platelets may be administered to cancer patients whose ability to produce platelets has been destroyed by chemotherapy and/or radiation treatment. RBCs may be administered to patients who have experienced rapid blood loss, or to improve the oxygen carrying capability of blood in patients suffering from anemia and the like.
It is now well known that viruses such as hepatitis B, hepatitis C, human immunodeficiency virus (HIV), cytomegalovirus and T-cell lymphotrophic virus (HTLV) may be resident within human blood and within the blood components. Certain bacteria such as Yersinia enterocolitica may also reside within human blood. The presence of virus and/or bacteria, (collectively referred to herein as "pathogens") in the blood stream poses the risk of infection and disease not only to the host, but also to a healthcare provider handling the blood, and/or if the collected blood or blood component is to be transfused, to the recipient of such blood or blood components. Accordingly, the medical community has attempted to reduce the risk of transfusing blood that contains such pathogens by developing methods and apparatus to remove or inactivate pathogens found in the blood component. As used herein, "pathogen inactivation" (and forms thereof) means, generally, rendering a pathogen harmless to a living being. Pathogen inactivation includes killing, destroying, or eradicating a pathogen (either viral or bacterial), or either directly or indirectly inhibiting the ability of the pathogen to replicate. "Pathogen inactivating compounds" refers to compounds used in pathogen inactivation, including the decomposition products of such compounds.
One early attempt of removing virus from blood involved the filtration of blood and blood components to remove intracellular viruses entrained, for example, in white blood cells, Rawal et al., "Reduction of Human Immunodeficiency Virus-Infected Cells From Donor Blood by Leukocyte Filtration," Transfusion, pages 460-462 (1989).
Other prior methods for inactivating viruses and, in particular, extracellular viruses in blood, include steam sterilization of blood plasma and use of "detergents" to cleanse the blood or the blood component of the pathogens.
Pathogen inactivation has also been proposed by treating blood or blood components with a photochemical agent and light, referred to as "photoactivation". When activated by light of an appropriate wavelength, the photochemical agent either kills the virus directly or indirectly inhibits the ability of the virus to replicate and, thus, in either case "inactivates" the virus. Several known photochemical agents have been used or disclosed for use in inactivating viruses in blood, including psoralens, as described in U.S. Pat. No. 5,459,030; pthalocyanines, as described, for example in Rywkin, S. et al. Photochem. Photobiol. 60:165-170 (1994); and phenothiazine dyes, including without limitation, toluidine blue O, azure A, azure B. azure C, thionine, methylene blue and dimethylmethylene blue. For example, U.S. Pat. No. 5,527,704, incorporated by reference herein, discloses methods and apparatus for inactivating viruses in biological fluid in which a biological fluid (e.g., plasma) is combined with methylene blue and subjected, for a period of time, to light of a suitable intensity and wavelength for activating the methylene blue.
Other methods for treating biological fluid such as blood or blood components which do not involve photoactivation are also known. For example, International Publication No. WO98/070674 describes mustards linked to aziridines. U.S. Pat. Nos. 5,691,132 and 5,559,250 (which are incorporated by reference herein) describe methods for treating a biological fluid that includes RBCs by contacting the RBCs with a compound having a nucleic acid binding ligand and a mustard group. It is believed that such compounds react with nucleic acids of the pathogen (both viral and bacterial) to form covalent complexes that inhibit replication of the pathogen. Examples of acridine compounds include, but are not limited to, compounds such as N1, N1-bis (2-chlorethyl)-N4-(6-chloro-2-methoxy-9-acridinyl)-1,4 pentanediamine.
It may also be desirable to include certain other organic compounds in the above described treatment system to enhance the effectivity of the pathogen inactivating compound by reducing or "quenching" potential side reactions of the pathogen inactivating compound. For example, inclusion of certain naturally occurring tripeptides such as, but not limited, to reduced L-glutathione quenches potential side reactions and allows for maximum pathogen inactivation by the pathogen inactivating compound. Other examples of quenchers useful in pathogen inactivation processes may include sulfydryls such as mercaptoethanol, as described in Rywkin, S. et al. Transfusion 35:414-20 (1995), cystein, quercitin, as described in Ben-Hur et al, Photochem. Photobiol 57:984-8 (1993) and rutin, as described in Margolis-Nunno, Transfusion 35:852-862 (1995).
As many of the pathogen inactivation methods known to date involve addition of either (1) compounds not normally present in blood (e.g., photochemical dyes, nucleic acid binding agents with mustard groups) or (2) concentrations of compounds (e.g., L-glutathione) in excess of typical concentrations found in human blood, it is desirable to remove substantially as much of the added compounds as possible from the treated biological fluid, prior to transfusion to a patient or other recipient.
For example, methods and devices for separating photoactive agents used in pathogen inactivation are described in U.S. Pat. No. 5,660,731. In that patent, photochemical agents such as methylene blue are separated from blood by contacting the photochemical agent with a porous medium that includes, for example, activated carbon fibers. The porous medium may be in the form of a web, sheet, cylinder or included in a filter with an inlet and outlet through which the biological fluid passes and, thus, contacts the porous medium.
A similar approach is described in U.S. Pat. No. 5,639,376 which discloses a filter for removing leukocytes and a viral inactivating agent such as methylene blue, its metabolites and photodecomposition products, from plasma or other blood fractions. As in U.S. Pat. No. 5,660,731, removal of the antiviral agent is achieved by contacting the blood with a filter adapted for removing, for example, both leukocytes and the antiviral agents. The filter includes activated carbon as a sorbent for methylene blue.
U.S. Pat. No. 4,728,432 more generally describes methods and devices for removing poisonous substances contained in blood by means of sorption. The sorbents described in that patent include, for example, activated carbon fixed to a support member. The activated carbon is combined with a polymer.
Other examples of methods and devices for removing organic compounds from a biological fluid are described in U.S. patent application Ser. No. 09/003,113, now abandoned, entitled "Methods and Devices for the Reduction of Small Organic Compounds from Blood Products" which is incorporated by reference herein. That application describes using sorbent particles such as activated carbon beads applied to a support for removal of, for example, acridine, acridine derivatives, methylene blue or thiols in a blood product. The activated carbon beads may be contained within a pouch or overwrap, or captured within a fiberized matrix, or captured within a fiberized matrix and contained within a pouch or overwrap.